Progress in Photovoltaics最新文献

PL-based external radiative efficiency (ERE) and implied open-circuit voltage (iV_OC) metrics were introduced for thin-film solar absorbers to better understand the voltage deficit and diagnose losses in solar cells. Traditionally, elevated ERE and iV_OC measurements are associated with diminished recombination within the solar device, a rationale heavily reliant on the assumption of a uniform bandgap and high carrier mobilities in the absorber. Recently, very low mobilities in CdSeTe absorbers (< 1 cm²/(V·s)) were measured using the light-induced transient grading technique. In this study, we use a detailed numerical model of iV_OC to investigate the possible reasons of elevated iV_OC in realistic CdSeTe absorbers with a graded Se profile. In particular, we examine how the bandgap nonuniformity and the reduced hole mobility in graded CdSeTe absorbers affect iV_OC measurements. We show that high iV_OC may result from inflated quasi-Fermi level splitting in the high-Se region in the front part of a CdSeTe absorber with slow hole transport. We reproduce the experimentally reported 360 mV increase in iV_OC–V_OC gap with reduced doping using a model with sub-1 cm²/(V·s) hole mobility in the high-Se region. Based on our results, we conclude that the iV_OC metric (or ERE metric) should not be used as a sole metric of CdSeTe absorber quality. We discuss possible ways to extract useful information from the iV_OC–V_OC gap by supplementing the front-side illumination measurements with back-side illumination measurements.

Potential-induced degradation (PID) presents a significant challenge to the long-term reliability of perovskite solar cells (PSCs) in commercial applications. Research on PID in PSCs is still in its early stages, and the polarization-type PID (PID-p) remains poorly understood. In this study, we used advanced microscopic techniques to investigate the underlying mechanisms of PID-p in PSCs. After 100 h of PID stress, the devices experienced severe performance loss, with efficiency reduced to 20.9% of its initial value. This degradation was primarily driven by a decrease in short-circuit current and fill factor, while the open-circuit voltage remained relatively stable. Our findings reveal that the accumulation of sodium ions at the glass/film interface triggers the formation of an electron inversion layer at the perovskite's bottom, leading to performance decline. Electrical and mechanical characterizations further confirm changes in material properties, particularly at the hole transport layer/perovskite interface, contributing to the degradation.

In photovoltaic applications, the rear surface morphology of tunnel oxide passivated contact (TOPCon) solar cells plays a critical role in their performance. However, traditional textured and polished surface morphologies both have limitations. This study introduces a hybrid nano-pyramid/polish morphology, combining a nano-pyramid structure on a polished surface. This new design aims to capitalize on the advantages of both textured and polished surfaces, achieving an optimal balance for TOPCon performance. The balance is achieved through an additional chemical solution treatment process. When applied to TOPCon solar cells, the hybrid structure outperforms both secondary-textured and polished morphologies in terms of optical absorption, passivation, and contact performance. The nano-pyramid/polish hybrid achieves a superior balance between light trapping, passivation, and contact quality. Furthermore, the study investigates the impact of rear surface morphology on film blistering, revealing that rougher surfaces are less prone to blistering. This is likely due to more favorable stress distribution in the SiO_x/poly-Si stack, enhancing mechanical stability. These findings demonstrate the compatibility of the hybrid nano-pyramid/polish morphology with TOPCon solar cells, offering a promising pathway to enhance efficiency. The insights gained may also benefit the development of other high-performance solar cell technologies, such as heterojunction (HJT) and silicon/perovskite tandem solar cells, advancing industrial photovoltaic applications.

Solar cells fabricated from short-carrier lifetime materials face efficiency limitations because of high recombination rates, particularly within the depletion region. Kesterite solar cells offer a promising alternative to conventional solar cells but suffer from short-carrier lifetimes. This work introduces a comprehensive analytical model applicable to such solar cells. We developed a novel approach to accurately represent the recombination rates of the carriers within the depletion region using a Gaussian function. This model overcomes the limitations of existing approximations and enables more precise dark current calculations. Additionally, we employed a fully analytical generation rate calculation based on the transfer matrix method for accurate photocurrent determination. The effectiveness of this model was validated by comparing its results with simulated and experimental data for kesterite solar cells, demonstrating excellent agreement in dark current and photocurrent, with maximum percentage errors of 1.9% and 1.7%, respectively. Beyond accuracy, the model also achieved a 75-fold improvement in computation speed compared to finite element method simulations. This highlights the effectiveness of the model in capturing the complex recombination processes within kesterite solar cells and in providing a valuable tool for understanding and optimizing the performance of solar cells based on short-lifetime materials, particularly kesterite-based devices with one-sided junction characteristics.

Obtaining high-quality repeatability data is the basis for improving measurement precision. Due to the inherent instantaneous fluctuation nature of field test conditions, obtaining high quality repeatability measurement results of photovoltaic (PV) modules in the field is still challenging. In this paper, firstly, we defined repeatability of PV modules measurement in the field, including repeatability and relative repeatability of measured and standard test conditions (STC)-corrected electrical parameters for fielded PV modules. Because STC is quite difficult to directly obtain outdoors, the correction procedure 4 in IEC 60891:2021 is used to obtain module STC characteristics. Then, the effect of the correction procedure on repeatability of electrical parameters of PV modules in the field was studied. The results show that repeatability of electrical parameters is changed before and after correction process. The variation reason was revealed by the established repeatability error propagation model. It is remarkable that there exist module maximum power point offsets before and after module characteristics correction. Moreover, the covariance terms contribute significantly to repeatability variation for fielded PV modules. Finally, the effect of field test conditions variation on repeatability of electrical parameters of PV modules was studied. The relative repeatability precision of module STC maximum power between field and indoor measurements was also compared. It is found that there is a greater probability to obtain indoor-level repeatability results within 0.7–1.0 kW/m² irradiance ranges (3.29%–5.04%) than that within 0.3–0.7 kW/m² irradiance ranges (0.47%–2.90%) for PV measurements in the field. The obtained results in this paper can provide new insights into precise performance measurement of PV modules under dynamic outdoor environmental conditions.