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Electronic and Optoelectronic Studies of Organic Semiconductors

Thesis Info

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Author

Khan, Dil Nawaz

Program

PhD

Institute

Ghulam Ishaq Khan Institute of Engineering Sciences and Technology

City

Swabi

Province

KPK

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1277

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726047793

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Organic semiconductors have made inroad into many area of devices which was formally dominated by inorganic semiconductors because of their wide variety of electronic and optoelectronic properties. They being low cost, light weight and low temperature processing materials provide opportunities to fabricate the variety of devices, such as, solar cells, field effect transistors, lasers, light emitting diodes, sensors, photo detectors, smart windows, large area displays, e-paper, etc. The material manipulation, low cost fabrication techniques and the emerging ideas are bringing about much improved performances in the organic electronic devices. Most of the earlier studies have been reported on the p-type organic semiconductors and little is known about n-types. In the development of future organic electronic industry, all organic complementary circuits are not possible without the availability of both p- and n-type organic semiconductors and data is required on the junction properties and mobility studies of these materials. Plenty of data is available on the junction diodes of p-type organic semiconductors but little is known on the n-type organic semiconductors based junction devices and mobility investigations. In this dissertation, the n-type organic semiconducting materials formyl- TIPPCu(II), N,N ́-di-n-heptyl-2,3:6,7-anthracenetetracarboxydiimide (ADCI7) and N,N ́- di-n-octyl 2,3,6,7 anthracenetetracarboxydiimide (ADCI8) have been investigated as active organic materials for their potential application in organic electronic devices. Using organic semiconductor formyl-TIPPCu(II), junction diode, temperature, light and humidity sensors have been fabricated, while ADCI7 and ADCI8 have been used for the fabrication of n-channel organic thin film transistors. To investigate junction properties of formyl-TIPPCu(II) organic semiconductor, fabrication of Ag/formyl-TIPPCu(II)/p-Si heterojunction diode was undertaken and it was made successfully. Its temperature dependent electrical properties are reported. The values of series resistance, ideality factor, zero bias barrier height are observed strongly dependent on temperature. The series resistance and ideality factor decease while the zero bias barrier height increases with the rise in temperature. viiThe surface type Ag/formyl-TIPPCu(II)/Ag humidity sensors has been fabricated to study the effects of changing relative humidity on the electrical parameters and their frequency dependant responses. The values of capacitance and resistance of the sensors were measured at different humidity levels at frequencies of 1 kHz, 10 kHz and 100 kHz. An increase in capacitance and decrease in resistance were observed during the rise of relative humidity from 45 to 95% RH. The hysteresis response of these humidity sensors was also studied at the frequency of 1 kHz. Effects of temperature and light are studied on the capacitance and resistance of the Au/formyl-TIPPCu(II)/Au device. The relative capacitance of the fabricated sensor increased by 4.3 times by rising temperature from 27 to 187 0 C, while under illumination up to 25000 lx, the capacitance of the Au/formyl-TIPPCu(II)/Au photo capacitive sensor increased by 13.2 times as compared to dark conditions. ADCI7 and ADCI8 were used to fabricate n-channel organic thin film transistors (OTFTs) on oxidized silicon wafers. To get the high performance of the devices and to avoid the trapping of charge carriers, the dielectric surface were modified by developing the buffer layer of PMMA or by self assembly monolayer (SAM) of HMDS. The OTFTs exhibited high charge mobility of the order of 10 -2 cm 2 V -1 S-1 (ADCI7) and 10 -3 cm 2 V -1 S - 1 (ADCI8) with the on/off ratio of the order of 10 4 showing the appreciable enhancement in the field effect properties of these materials as compared to the previously reported researches for the same family of materials. ADCI7 is introduced as new compound for high mobility n-channel OTFTs.
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تمنا ئے دیدارِ مرشد

تمنا ئے دیدار مرشد
تیرے شہر میں ہم بھی آئیں گے
قسمت نے دیا ساتھ تو دیدار بھی پائیں گے

تیرے شہر کی بہاریں بہت یاد آتی ہیں
تیری مخمور نگاہیں دل پہ تیر چلاتی ہیں
تیری ادائیں مجھ کو بہت ہی بھاتی ہیں
تیرے شہر میں ہم بھی نشیمن بنائیں گے

ہم ترس رہے ہیں تیرے دیدار کے لیے
ہم مارے مارے پھر رہے ہیں تیرے پیار کے لیے
ہم تڑپ رہے ہیں تیری محفل کے انوار کے لیے
کبھی تو تیری محفل میں دل کی پیاس بجھائیں گے

ہمارے شہر میں پیاء جب تشریف لائیں گے
غم زدہ لوگ غم کی داستان سنائیں گے
نگاہِ لطف و کرم جب وہ ہم پہ فرمائیں گے
ہمارے دل بھی خوشی سے جھوم جائیں گے

محبوب سے ہم بیٹھے ہیں بہت دور
مگر دل ملنے کو ہوا ہے مجبور
قسمت میں لکھا ہے تو ملیں گے ضرور
ان کو ملنے کے لیے ہم ان کے کوچہ میں جائیں گے

چاولہ سائیں ان کی ملاقات ہوہی جائے گی
حوصلہ رکھ نہ گھبرا رحمت کی برسات ہوہی جائے گی
سب مہربانوں سے مہربان رب کی ذات ہوہی جائے گی
اک دن وصل شراب محبوب ہمیں بھی پلائیں گے

Social Media Policies of Medical Colleges of Pakistan

Introduction: A total of 144 medical colleges are contributing to the country’s progress. Excessive usage of social media is a cause of not only the deterioration of physical and psychological health of medical students, but has also become a defining reason of procrastination and attaining less than ideal grades. Where most western institutes implement strict social media policies in medical schools, those in Pakistan are gravely lacking. Objective: The objective of this research implementation of social media in medical schools of Pakistan and then identify the need to develop such policies. Methods: We conducted qualitative research in which method of data collection was primarily focus group discussions (FGD) of a total of 40 participants from five different medical colleges of Pakistan. The participants included medical practitioners and medical students(n=20) who were further divided into four groups of five participants each. FGD was conducted online. Results: Content analysis revealed seven core themes as point of discussions to be highlighted. Almost all participants were grossly unaware of the importance of social media usage regulation and its implementation in medical schools. Conclusion: At the end of the FGD it was unanimously agreed upon that there must be a uniform and standard social media policy defined by the regulating bodies of medical schools. This research may further be conducted by including policymakers in the sample. KEYWORDS: Social media, policy, medical colleges.

Investigation on Intercropping of Ziziphus Mauritiana With Cajanus Cajan for Fruit and Fodder at Marginal Land and Cultivation of Carissa Carandas for Fruits Through Saline Water Irrigation

Salinity is a growing threat to crop production which affects sustainability of agriculture in arid/semiarid areas. Growth responses of plant to salinity vary considerably among species. Cajanus cajan, Ziziphus mauritiana and Carissa carandas are sub-tropical crops, grown worldwide particularly in Asian subcontinent for edible and fodder purposes but not much is known about their salinity tolerance and intercropping. Effect of salinity has been initially studied in present work at germination of C. cajan under different sea salt salinities using presoaked seeds with water and respective salt solutions. Seed germination decreased with increasing salinity and it was more sever in presoaking under water of different salinities. The 50% threshold reduction started at ECiw= 3.5 dSm-1 sea salt in presoaking treatments. However, this threshold was decreased up to ECiw= 16.8 dSm-1 sea salt at further seedling establishment stage. Growth experiment of C. cajan in drum pot culture (Lysimeter) also showed a salt induced growth reduction in which plant tolerate salinity up to 4.2 dSm-1. At this salinity, leaf pigments (chlorophylls and carotenoids), proteins and insoluble sugars decreased up to 50% whereas, soluble sugars were increased (~25%). Reproductive growth was also affected at this salinity, in which at least 70% reduction in flowers, pods and seeds were observed. Salt tolerance of symbiotic nitrogen fixing bacteria associated with root of C. cajan showed salinity tolerance up to ECw= 36.6 dSm-1 NaCl salinity invitro environment. For intercropping experiments, Ziziphus mauritiana (grafted variety) was selected with C. cajan. Preliminary investigations showed a growth promotion in Z. mauritiana at low salinity (ECe= 7.2 dSm-1) and growth was remained unaffected up to ECe= 11.1 dSm-1. Intercropping of C. cajan with Z. mauritiana was primarily done in drum pot (Lysimeter) culture. Result showed better growth responses of both species when growing together as intercrops than sole in which encouraging results were found in 8th day irrigation interval rather than of 4th day. Biochemical parameters e.g. photosynthetic pigments, protein, phenols, electrolyte leakage and sugars of these species displayed increase or decrease according to their growth responses. Increased activity of antioxidant enzymes and that of nitrate reductase and its substrate (NO3) also contributed in enhancement of growth. Field experiment of intercropping of above mentioned plants at marginal land irrigated with underground water (Eciw= 2.8 dSm-1) showed better vegetative growth of both species than sole crop. The overall reproductive growth remained unaffected, although, the numbers, size and weight of fruit were better in intercropping system. Photosynthetic pigments were mostly increased, whereas, leaf protein and sugars remained unchanged. In addition, higher values of LER and LEC (> 1) indicated the success of intercropping system. Experiment on salinity tolerance of Carissa carandas (varn. karonda) using drum pots culture showed improvement at low salinity (up to ECiw= 4.2 dSm-1 sea salt) whereas, higher salinity (ECiw= 12.9 dSm-1 sea salt) adversely affected vegetative and reproductive growth. Plant managed to tolerate up to ECiw= 9.9 dSm-1 sea salt. Salinity severely affected biochemical parameters including photosynthetic pigments, proteins and sugars, whereas leaf phenolics were increased. Leaf accumulated high amount of Na+ whereas, affect absorption of essential minerals like K+ was decreased. In the light of above mentioned investigations, it appears that, C. cajan can be propagated in saline soils with good presoaking techniques in non-saline water which would helped to grow at moderately saline conditions. It could be a good option used as intercrop species because of its ability to improve soil fertility even under water deficit conditions. The proposed Cajanus-Ziziphus intercropping system could help poor farmers to generate income from unproductive soils by obtaining sufficient fodder from C. cajan for their cattle and producing delicious edible fruits from Z. mauritiana for commercial purposes. Carissa carandas could also be introduced as new crop for producing fruits from moderate saline waste lands and used for preparing prickle, jam, and jelly for industrial purposes.