Effect of Sn Doping of Sol-gel Processed ZnO Electron Transport Layer on the Photovoltaic Performance in P3HT:PCBM-based Organic Solar Cell

Abstract

inc Oxide (ZnO) films made at low temperature by sol-gel process are one of the best electron transporting layers (ETLs) for high-performance organic solar cells (OSCs) due to the absence of pinholes, ease of preparation, thickness controllability, and processability at low temperature. The charge mobility and electrical conductivity of ZnO films prepared at low temperatures, on the other hand, are lower, resulting in a decrease in photovoltaic performance. In this work, pristine and Sn-doped ZnO thin films were prepared via the sol-gel method at a low temperature as electron transporting layers (ETLs) in poly (3 hexylthiophenes) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blend OSCs device. To investigate the effect of Sn dopant on the properties of ZnO thin films, the dopant concentrations varied from 1 %, 2 %, 3 %, and 5 % weight percentages. The highest power conversion efficiency (PCE) of about 3.45 % was measured on the sample with a 3 wt. % of Sn dopant, which is an increase of almost 340 % compared to the PCE of the ZnO-only device (1.01 %). It was found that Sn-doped ETL exhibited an improvement in electrical conductivity by more than two folds and reduced electron trapping defect states which is beneficial for enhanced transport of the dissociated electron from the active layer. Moreover, the device with Sn-doped ZnO exhibited an enormous improvement in exciton generation and dissociation efficiency in addition to enhanced charge mobility, especially for the device at an optimum dopant concentration of 3 wt.%. The combined effect of all these properties attributed to an increment of current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) by 200 %, 140 %, and 130 %, respectively, in the 3 wt% Sn doped device compared to the reference device, resulting in improved photovoltaic performance. These results imply that Sn-doped ETLs enable efficient metal oxide ETL in P3HT-based OSCs, and we believe that the active layer is not limited to polymers used in this work and can also be used in flexible solar cell applications because of annealing at low-temperatures.

Inc Oxide (Zno) Films Made At Low Temperature By Sol-Gel Process Are One Of The Best Electron Transporting Layers (Etls) For High-Performance Organic Solar Cells (Oscs) Due To The Absence Of Pinholes, Ease Of Preparation, Thickness Controllability, And Processability At Low Temperature. The Charge Mobility And Electrical Conductivity Of Zno Films Prepared At Low Temperatures, On The Other Hand, Are Lower, Resulting In A Decrease In Photovoltaic Performance. In This Work, Pristine And Sn-Doped Zno Thin Films Were Prepared Via The Sol-Gel Method At A Low Temperature As Electron Transporting Layers (Etls) In Poly (3 Hexylthiophenes) And [6,6]-Phenyl-C61-Butyric Acid Methyl Ester (P3ht:pcbm) Blend Oscs Device. To Investigate The Effect Of Sn Dopant On The Properties Of Zno Thin Films, The Dopant Concentrations Varied From 1 %, 2 %, 3 %, And 5 % Weight Percentages. The Highest Power Conversion Efficiency (Pce) Of About 3.45 % Was Measured On The Sample With A 3 Wt. % Of Sn Dopant, Which Is An Increase Of Almost 340 % Compared To The Pce Of The Zno-Only Device (1.01 %). It Was Found That Sn-Doped Etl Exhibited An Improvement In Electrical Conductivity By More Than Two Folds And Reduced Electron Trapping Defect States Which Is Beneficial For Enhanced Transport Of The Dissociated Electron From The Active Layer. Moreover, The Device With Sn-Doped Zno Exhibited An Enormous Improvement In Exciton Generation And Dissociation Efficiency In Addition To Enhanced Charge Mobility, Especially For The Device At An Optimum Dopant Concentration Of 3 Wt.%. The Combined Effect Of All These Properties Attributed To An Increment Of Current Density (Jsc), Open-Circuit Voltage (Voc), And Fill Factor (Ff) By 200 %, 140 %, And 130 %, Respectively, In The 3 Wt% Sn Doped Device Compared To The Reference Device, Resulting In Improved Photovoltaic Performance. These Results Imply That Sn-Doped Etls Enable Efficient Metal Oxide Etl In P3ht-Based Oscs, And We Believe That The Active Layer Is Not Limited To Polymers Used In This Work And Can Also Be Used In Flexible Solar Cell Applications Because Of Annealing At Low-Temperatures.