Wide‐bandgap perovskite solar cells (PSCs) with an optimal bandgap between 1.7 and 1.8 eV are critical to realize highly efficient and cost‐competitive silicon tandem solar cells (TSCs). However, such wide‐bandgap PSCs easily suffer from phase segregation, leading to performance degradation under operation. Here, it is evident that ammonium diethyldithiocarbamate (ADDC) can reduce the detrimental I2 back to I− in precursor solution, thereby reducing the density of deep level traps in perovskite films. The resultant perovskite film exhibits great phase stability under continuous illumination and 30–60% relative humidity conditions. Due to the suppression of defect proliferation and ion migration, the PSCs deliver great operation stability which retain over 90% of the initial power conversion efficiency (PCE) after 500 h maximum power point tracking. Finally, a highly efficient semitransparent PSC with a tailored bandgap of 1.77 eV, achieving a PCE approaching 18.6% with a groundbreaking open‐circuit voltage (VOC) of 1.24 V enabled by ADDC additive in perovskite films is demonstrated. Integrated with a bottom silicon solar cell, a four‐terminal (4T) TSC with a PCE of 30.24% is achieved, which is one of the highest efficiencies in 4T perovskite/silicon TSCs.
Light soaking (LS) effect of perovskite solar cells (PSCs), i.e., the power conversion efficiency (PCE) increases under continuous light illumination (CLI), has attracted a lot of attention recently. Herein, it is reported that a strong LS effect occurs in the FAxMA1‐xPbI3 (FAMA) PSC for its PCE increases from 7.5% to 20.5% under CLI. Based on the dynamics of the LS effect, drift‐diffusion simulations, and external voltage experiments, it is found that the underlying process for the LS effect is that the generated photovoltage under CLI modulates the distribution of mobile ions in absorber layers increasing charge extraction ability and then alleviating interface recombination, which directly results in the LS effect in FAMA PSCs. In addition, the introduction of Cs+ into perovskite films can reduce the density of accumulated mobile ions at the interface between absorber layers and charge‐transporting layers in FAMA PSCs. As a result, the PCE of the Cs+‐doped device increases from 18.7% to 22.4% under CLI demonstrating that the LS effect in the Cs+‐doped device is suppressed notably. This work reveals the correlation of the LS effect with ion migration and suppresses the LS effect in FAMA PSCs.
Wide-bandgap (WBG) perovskite solar cells (PSCs) with high performance and stability are in considerable demand in the photovoltaic market to boost tandem solar cell e ciencies. Perovskite bandgap broadening results in a high barrier for enhancing the e ciency of the PSCs and causes phase segregation in perovskite. In this study, we show that the residual strain is the key factor affecting the WBG perovskite device e ciency and stability. The DMSO addition not only helps lead halide to with opening the vertical layer spacing to form (CsI)0.08(PbI1.4Br0.6) and (CsI0.125Br0.875)0.08(PbI1.2Br0.8) intermediate phases, but also provide more nucleation sites to eliminate lattice mismatch with FAX (X = I, Br or Cl) or MAX, which dominates the strain effects on the WBG perovskite growth in a sequential deposition. By minimizing the strain, 1.67-and 1.77-eV nip devices with record e ciencies of 22.28% and 20.45%, respectively, can be achieved. The greatly enhanced suppression of phase segregation enables the device with retained 90% -95% of initial e ciency over 4000 h of damp stability and 80% -90% of initial e ciency over 700 h of maximum-power-point output stability under full-spectrum light without encapsulation. Besides, the 1.67-eV pin devices can achieve a competitive 22.3% e ciency while achieving considerable damp-heat, pre-ultraviolet (pre-UV) aging, and MPP tracking stability as per the tests conducted according to IEC 61215. The nal e ciency for the perovskite/Si tandem is more than 28.3 %, which matches the top e ciencies reported to date.
Herein, it is demonstrated that low temperature current injection and annealing (CIA) treatment can cause evident improvements in open circuit voltage, short‐circuit current, and fill factor of tunnel oxide‐passivated contact (TOPCon) silicon solar cells, leading to a notable conversion efficiency gain (over 0.4% absolute at the best condition). The effects of injected current and annealing temperatures toward the improvement of electrical performance of the TOPCon solar cells are compared. The more evident increase in the electrical performance after the CIA treatment may come from the higher fill factor improvements, which can be induced by the change of contact resistance after the CIA treatment, the potential involvement of hydrogen is discussed. The CIA treatment can be a reliable approach to further enhance the conversion efficiency of TOPCon solar cells, which is of great significance for the global PV industry.
Intrinsic hydrogenated amorphous silicon (a-Si:H) film has been demonstrated to hydrogenate dangling bonds on the surface of crystalline silicon (c-Si), which reduces the interface defect density, thus enabling an outstanding passivation effect [1-3]. However, like many other industrial c-Si solar cells that suffer from light-induced degradation and light and elevated temperature induced degradation (LeTID) [4,5], the decay of electrical properties has also been found in thin-film a-Si:H solar cells , as well as samples of c-Si coated with intrinsic a-Si:H films after light soaking . A significant observation reported by Plagwitz et al.  suggested that illumination induced an increase in surface recombination velocities for both a-Si:H coated p-type and n-type c-Si substrates. The degradation of performance is generally attributed to the generation of deeplevel defects acting as recombination centers, most likely as single dangling bonds [11,12], which is considered to be related to the Staebler-Wronski effect (SWE) .However, when a-Si:H film is doped and overlays with another thin intrinsic a-Si:H film (Fig. S1), the functionality of silicon heterojunction (SHJ) cells can be further increased because of the carrier selectivity possessed by the n-type and ptype a-Si:H overlayers, which efficiently help to collect electrons and holes, respectively [14,15]. Such a structure of c-Si coated with doped/intrinsic a-Si:H bilayers is the key component of SHJ solar cells. Compared with the high fabrication temperature of conventional c-Si solar cells (up to 900°C), SHJ solar cells usually require a relatively low processing temperature (<200°C) when a-Si:H is deposited using plasma-enhanced chemical vapor deposition (PECVD) [16,17]. Due to the simple and low-cost manufacturing process, as well as its excellent passivation effect, the a-Si:H film has been widely used in SHJ solar cells. Tanaka et al.  proposed the p-a-Si:H/n-c-Si heterojunction structure with a thin intrinsic a-Si:H layer inserted in between, which achieved an efficiency (η) of 18.1% in 1992. Recently, Sai et al.  improved the open-circuit voltage (V OC ) of SHJ solar cells to 754 mV, and LONGi solar reported an η of 26.3% in 2021 (https://www.longi.com/cn/news/7093/).It is essential for solar cells to maintain their excellent properties during long periods of light soaking, which occurs in a normal working environment. Thus, understanding the longterm stability of SHJ solar cells is imperative. To date, several studies  have been conducted to investigate the stability
Herein, the degradation and regeneration processes of p‐type cast‐monosilicon passivated emitter rear contact solar cells are investigated, by taking open‐circuit voltage as a measure for the light‐ and elevated‐temperature‐induced degradation (LeTID) and regeneration extent. Degradation and regeneration are triggered by current injection and light soaking at the same temperatures. Then, an Arrhenius plot, derived from the proposed model, is used to extract the degradation and regeneration rate constants of LeTID during both current injection and light‐soaking processes. The activation energies of degradation processes are calculated to be (0.790 ± 0.064) and (0.828 ± 0.013) eV for current injection and light soaking, respectively. The corresponding activation energies for regeneration processes are (1.059 ± 0.112) and (1.179 ± 0.070) eV, respectively. Notably, the similar activation energies indicate that the root cause of the LeTID induced by current injection or light soaking is the same. In addition, an exponential dependence of the rate constants upon the injection current values during the whole degradation and regeneration cycle induced by current injection is observed. These results are not only significant for understanding the kinetics of LeTID but also can shed light on effective LeTID suppression method in the photovoltaic industry.
Passivated emitter and rear cell (PERC) solar cells have dominated the photovoltaic market in recent years. Continuously improving the efficiency of PERC solar cells is of great importance to enable the goal of low electricity cost, which is cheaper than the cost of thermal power generation. Herein, it is demonstrated that a two‐step postfiring bias treatment is able to evidently enhance the efficiency of commercial gallium‐doped PERC solar cells by up to 0.1% absolute. In detail, the first‐step bias treatment is done by forward biasing the PERC solar cells at 12 A and 200 °C for 60 min, resulting in an average efficiency enhancement at around 0.05% absolute. The second‐step bias treatment is done by reverse biasing the PERC solar cells at −0.1 or −0.2 V and at the elevated temperatures for certain times, leading to another average efficiency enhancement at around 0.05% absolute. To explore the mechanism underlying the two‐step bias treatments on improving cell efficiency, a new model in light of hydrogen behavior under electric field is proposed to explain this phenomenon.
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