• Energy Research

Abstract Here, we report an origin of loss in open circuit voltage (Voc) in perovskite solar cells due to the possible trap-assisted recombination within the widely used TiO2 compact layer (CL) and at its interface with FTO substrate. A thin layer (TL) of MgO was employed to investigate the recombination mechanism. MgO in place of TiO2 CL (50–60 nm) enhances Voc of the cell significantly while the MgO layer coated on TiO2 CL (TiO2-MgO bilayer) does not change the Voc much. In combination with open-circuit voltage decay (OCVD) measurements, we reveal that recombination at FTO/TiO2 interface is a major factor regulating the voltage and efficiency of TiO2-based perovskite solar cells.

In sequential deposition method of lead‐halide perovskite material, the PbI2 layer morphology and remnant PbI2 play an important role in enhancing the power conversion efficiency (PCE) of the perovskite solar cell. However, humidity levels affect the PbI2 and perovskite film morphology, resulting in defect sites and recombination centers on the surface and within the bulk of the material, thus impeding the overall device performance and stability. To address this, incorporation of tetrahydrofuran (THF) additive in PbI2–dimethylformamide (DMF) precursor solution is reported, to improve the quality of PbI2 thin films and to prevent the water interaction directly with PbI2 under high humidity environments. The O‐donor THF interacts with PbI2, resulting in a homogeneous, dense, and pinhole‐free layer as compared with the PbI2 layer without additive. The perovskite layer so obtained from the pinhole‐free PbI2 layer is compact, resulting in a significant reduction of defects/traps. The device is fabricated with modified perovskite in ≈50% humidity atmosphere, resulting in 15% efficiency with high reproducibility. Moreover, the THF‐modified non‐encapsulated perovskite device retains 80% PCE after exposure to 50% relative humidity for 20 days. A strategy to fabricate perovskite solar cells, with reproducible efficiency in high humidity atmosphere viable for large‐scale production, is demonstrated.

Controlling the morphological structure of titanium dioxide (TiO2) is crucial for obtaining superior power conversion efficiency for dye‐sensitized solar cells. Although the sol–gel‐based process has been developed for this purpose, there has been limited success in resisting the aggregation of nanostructured TiO2, which could act as an obstacle for mass production. Herein, we report a simple approach to improve the efficiency of dye‐sensitized solar cells (DSSC) by controlling the degree of aggregation and particle surface charge through zeta potential analysis. We found that different aqueous colloidal conditions, i.e., potential of hydrogen (pH), water/titanium alkoxide (titanium isopropoxide) ratio, and surface charge, obviously led to different particle sizes in the range of 10–500 nm. We have also shown that particles prepared under acidic conditions are more effective for DSSC application regarding the modification of surface charges to improve dye loading and electron injection rate properties. Power conversion efficiency of 6.54%, open‐circuit voltage of 0.73 V, short‐circuit current density of 15.32 mA/cm2, and fill factor of 0.73 were obtained using anatase TiO2 optimized to 10–20 nm in size, as well as by the use of a compact TiO2 blocking layer.

Abstract Large-area integrated modules of flexible plastic type dye-sensitized solar cell (DSC) have been fabricated based on polyethylene naphthalate (PEN) film for practical applications such as ubiquitous power sources. From the view point of improving durability, composition of organic solvent-based electrolytes has been investigated. As a result, a plastic DSC module using LiI-free electrolyte maintained its energy conversion efficiency of 2% over 220 h under the accelerated condition of 55 °C and 95% relative humidity.

AbstractWe have successfully demonstrated solar water splitting using a newly fabricated photoelectrochemical system with a Pt‐loaded SiC photocathode, a CoOx‐loaded BiVO4 photoanode, and a perovskite solar cell. Detection of the evolved H2 and O2 with a 100 % Faradaic efficiency indicates that the observed photocurrent was used for water splitting. The solar‐to‐hydrogen (STH) efficiency was 0.55 % under no additional bias conditions.

AbstractIt is well known that the surface trap states and electronic disorders in the solution‐processed CH3NH3PbI3 perovskite film affect the solar cell performance significantly and moisture sensitivity of photoactive perovskite material limits its practical applications. Herein, we show the surface modification of a perovskite film with a solution‐processable hydrophobic polymer (poly(4‐vinylpyridine), PVP), which passivates the undercoordinated lead (Pb) atoms (on the surface of perovskite) by its pyridine Lewis base side chains and thereby eliminates surface‐trap states and non‐radiative recombination. Moreover, it acts as an electron barrier between the perovskite and hole‐transport layer (HTL) to reduce interfacial charge recombination, which led to improvement in open‐circuit voltage (Voc) by 120 to 160 mV whereas the standard cell fabricated in same conditions showed Voc as low as 0.9 V owing to dominating interfacial recombination processes. Consequently, the power conversion efficiency (PCE) increased by 3 to 5 % in the polymer‐modified devices (PCE=15 %) with Voc more than 1.05 V and hysteresis‐less J–V curves. Advantageously, hydrophobicity of the polymer chain was found to protect the perovskite surface from moisture and improved stability of the non‐encapsulated cells, which retained their device performance up to 30 days of exposure to open atmosphere (50 % humidity).