Sources of Thermal Power Generation and Their Influence on the Operating Temperature of Organic Solar Cells.

Hooman Mehdizadeh-Rad,Farhad Mehdizadeh-Rad,David Ompong,Naveen Kumar Elumalai,Jai Singh,Furong Zhu,Daniel Dodzi Yao Setsoafia,Kiran Sreedhar Ram

doi:10.3390/nano12030420

Abstract

Thermal stability, closely associated with the operating temperature, is one of the desired properties for practical applications of organic solar cells (OSCs). In this paper, an OSC of the structure of ITO/PEDOT:PSS/P3HT:PCBM/ZnO/Ag was fabricated, and its current-voltage (J-V) characteristics and operating temperature were measured. The operating temperature of the same OSC was simulated using an analytical model, taking into consideration the heat transfer, charge carrier drift-diffusion and different thermal generation processes. The simulated results agreed well with the experimental ones. It was found that the thermalization of charge carriers above the band gap had the highest influence on the operating temperature of the OSCs. The energy off-set at the donor/acceptor interface in the bulk heterojunction (BHJ) was shown to have a negligible impact on the thermal stability of the OSCs. However, the energy off-sets at the electrode/charge-transporting layer and BHJ/charge-transporting layer interfaces had greater impacts on the operating temperature of OSCs at the short circuit current and maximum power point conditions. Our results revealed that a variation over the energy off-set range from 0.1 to 0.9 eV would induce an almost 10-time increase in the corresponding thermal power generation, e.g., from 0.001 to 0.01 W, in the cells operated at the short circuit current condition, contributing to about 16.7% of the total solar power absorbed in the OSC.

Highlights

Organic solar cells (OSCs) have achieved very rapid developments over the last decade, as they are light weight, flexible, and economical to fabricate due to their low temperature solution processing [1,2,3,4,5,6]
The simulated operating temperature and J-V characteristics of the organic solar cell considered in this work were validated by comparing with the corresponding experimental results
The results show that among all the internal thermal power-generating factors, the thermalization of charge carriers above the band gap had the highest influence on the thermal stability and operating temperature of the organic solar cell

Summary

Introduction

Organic solar cells (OSCs) have achieved very rapid developments over the last decade, as they are light weight, flexible, and economical to fabricate due to their low temperature solution processing [1,2,3,4,5,6]. The experimental power conversion efficiency (PCE) of OSCs has reached over 18% [7]. To accomplish commercialization, their PCE and stability should be comparable with the commercially available inorganic solar cells [8,9,10,11]. There are various factors that affect the PCE and stability of OSCs, among which the operating temperature plays one of the crucial roles [12,13,14]. Katz et al [16] have investigated the influence of operating temperature on the performance of polymer-fullerene-based solar cells. According to Tvingstedt et al [17], the ideality factor of OSCs is temperature-dependent, and it provides necessary information about the main charge

Methods

Results

Conclusion