Charge transport studies in donor-acceptor block copolymer PDPP-TNT and PC71BM based inverted organic photovoltaic devices processed in room conditions

Shashi B Srivastava,Samarendra P Singh,Prashant Sonar

doi:10.1063/1.4927763

Shashi B Srivastava, Samarendra P Singh + Show 1 more

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https://doi.org/10.1063/1.4927763

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Abstract

Diketopyrrolopyrole-naphthalene polymer (PDPP-TNT), a donor-acceptor co-polymer, has shown versatile behavior demonstrating high performances in organic field-effect transistors (OFETs) and organic photovoltaic (OPV) devices. In this paper we report investigation of charge carrier dynamics in PDPP-TNT, and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) bulk-heterojunction based inverted OPV devices using current density-voltage (J-V) characteristics, space charge limited current (SCLC) measurements, capacitance-voltage (C-V) characteristics, and impedance spectroscopy (IS). OPV devices in inverted architecture, ITO/ZnO/PDPP-TNT:PC71BM/MoO3/Ag, are processed and characterized at room conditions. The power conversion efficiency (PCE) of these devices are measured ∼3.8%, with reasonably good fill-factor 54.6%. The analysis of impedance spectra exhibits electron’s mobility ∼2 × 10−3 cm2V−1s−1, and lifetime in the range of 0.03-0.23 ms. SCLC measurements give hole mobility of 1.12 × 10−5 cm2V−1s−1, and electron mobility of 8.7 × 10−4 cm2V−1s−1.

Highlights

Bulk heterojunction based organic photovoltaic (OPV) devices have witnessed significant improvement in their performance up to ∼10% over last few years.[1,2] In order to harness potential applications of OPV devices towards realizing low-cost, low-temperature processable and flexible solar cells, intense efforts are being made.[3]
In this paper we report investigation of charge carrier dynamics in PDPP-TNT, and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) bulk-heterojunction based inverted OPV devices using current density-voltage (J-V) characteristics, space charge limited current (SCLC) measurements, capacitance-voltage (C-V) characteristics, and impedance spectroscopy (IS)
We report an investigation of charge dynamics in PDPP-TNT:PC71BM bulk heterojunction based inverted OPV devices processed and characterized under room conditions

Summary

INTRODUCTION

Bulk heterojunction based organic photovoltaic (OPV) devices have witnessed significant improvement in their performance up to ∼10% over last few years.[1,2] In order to harness potential applications of OPV devices towards realizing low-cost, low-temperature processable and flexible solar cells, intense efforts are being made.[3] These efforts are focused around developing high performing air-stable organic small molecules and polymers, and optimizing device performances by introducing different functional interfacial layers of organic or inorganic materials in conventional or inverted device structures.[4,5] Inverting the device architecture makes OPVs less prone to ambient degradation and offers better air-stability by opening more choices of materials.[6,7] Further, an in-depth investigation of dynamics and recombination kinetics of charge carriers is essential to know underlying physics of OPV devices.[5,8] A combination of characterization tools are needed to apply in order to establish the dependence of electrical parameters of OPV devices on the properties of individual organic materials, the morphology of bulk heterojunction active layers, and the energetics at various interfaces involved in devices We believe such studies will pave the way to understand existing device performance limiting factors, and to develop OPV devices into a mature technology.

EXPERIMENTAL DETAILS

EXPERIMENTAL RESULTS AND DISCUSSIONS

CONCLUSION