Evaluation of Polymer Solar Cell Efficiency To Understand the Burn-in Loss

Abstract

In this study, the degradation process of a conventional P3HT:PC 61 BM bulk heterojunction solar cell device due to light-induced aging is evaluated. This structure is chosen so as to reduce the number of interface layers. Continuous light aging is done under AM1.5G light, and devices are analyzed in short periods. The measured electrical properties, such as current−voltage, capacitance−voltage, and capacitance−frequency characteristics, and optical and structural properties suggested the process of device degradation progression. In order to investigate the photodegradation of the device and the trap state formation, various device parameters are determined, such as the density of trap states, trap distribution width, peak trap state position, carrier concentration, and built-in potential. The dual peak nature is observed in the capacitance−voltage spectra of the light-aged device. Formation of defect peaks should be attributed to trap states as well as morphological changes: modification at the donor/acceptor and semiconductor/electrode interface. Additionally, the defect peak intensity increases as the light aging period increases. The calculated carrier concentration and density of trap states are observed to be correlated with the device performance. The detailed analysis of the device properties indicates that interface-induced changes are the initial points of device degradation. The initial point of degradation primarily affects short-circuit current and fill factor (FF). Observed changes in the current density, J SC , and FF are mainly associated with an increase in the series resistance, R s . Structural and optical properties of as-prepared and aged devices revealed that there is not much change in the absorbance and crystallinity. These results corroborate that the initial device degradation is mainly due to the electrical part (various resistance) associated with the device. Further, the doublet in the capacitance spectrum under the illuminated condition is discussed. The burn-in loss of the solar cell is connected with an increase in the density of trap states. This work provides direct evidence of the formation of defect states in the device, which is portrayed in the capacitance−voltage spectra of aged samples under the illuminated condition.

Analysis of the degradation of highefficiency encapsulated PM6:Y7based Photovoltaic Cells

“…The normalized performance parameters detailed that have been investigated over time until reaching T1056. In Figure 2(a), the cells show a first, faster decay of PCE (approximately 7% of the starting value) in the initial hours from 0 h to 48 h. This atrophy is generally described as one of the degradation damage mechanisms, which is known as "burn-in loss" [7,8]. Subsequently, in the case of PCE, we can observe a sudden increase and a renewed downward trend.…”

Understanding the role of interfacial layers in the photostability of PM6:Y7-based organic solar cells under different degradation conditions

“…This behaviour is a degradation loss mechanism known as "burn-in loss" due to the photochemical reactions within the active layer affecting charge transport properties. 28,29 The non-encapsulated devices lose 20% of their initial PCE before 24 h (T 80 ), faster than encapsulated devices which took 336 h. The poor stability of non-encapsulated NFA-OSCs is related to water and oxygen under ambient conditions degrading the electrode interfaces and reducing the electrical properties of the active layer of OSCs. 30,31 Aer 1000 h, the PCE of devices under a N 2 atmosphere remained at 88% of its initial value.…”

Enhancing optical absorption by reducing the trap states in polymer semiconductor processed for solar cell

“…In general, polymer solar cell requires the following properties (i) wide range optical absorption (ii) higher charge carrier mobility and so on. Optical absorption can be improved by synthesizing low band gap polymeric semiconductor (Lu and Yu, 2014;Kesavan et al, 2019), increasing degree of crystallinity of the polymer (Zhang et al, 2019;Nellissery Viswanathan et al, 2022), increasing thickness of the active layer. But increasing active layer thickness will increase series resistance and also.…”

“…These processes modify the spatial reorganization of the polymer chain and fullerene molecule. Solar cell device performance mainly depends on the active layer deposition condition from its blend solution and post deposition process such as solvent selection, thin film solidification rate, thermal annealing of solidified film, vapor annealing of active layer (Kesavan et al, 2019;Rao et al, 2018). Either pre-deposition process or post deposition process, the ultimate goal is to improve crystallinity in the blends layer and to get the optimum phase separation in P3HT and PC 61 BM.…”