Search

The surface morphologies, crystallinities, and excitonic characteristics of MAxCs1−xPb(IxBr1−x)3 thin films deposited on top of the P3CT‐Na/ITO/glass substrates are investigated by using the atomic‐force microscopic images, absorbance spectra, grazing incidence X‐ray diffraction patterns, photoluminescence (PL) spectra, and Raman scattering spectra. The P3CT‐Na‐based perovskite solar cell shows a stable and efficient maximum power density curve due to the formation of a graded MA0.83Cs0.17Pb(I0.83Br0.17)3 alloy thin film which is confirmed by using the surface‐sensitive PL and Raman scattering spectra. The highest power conversion efficiency (PCE) of the P3CT‐Na‐based MA0.83Cs0.17Pb(I0.83Br0.17)3 solar cells is 15.93% mainly due to the high fill factor of 79.4%. Besides, the PCE of the nonencapsulated solar cell slowly decreases to a moderate value (10.48%) within 157 days under an uncontrolled environment (55–60 relative humidity%) at room temperatures (22–25 °C). [ABSTRACT FROM AUTHOR]

The averaged power conversion efficiency of polyelectrolytes (P3CT-Na) based MAPbI3 solar cells can be increased from 14.94% to 17.46% with a wetting method before the spin-coating process of MAPbI3 precursor solutions. The effects of the wetting process on the surface, structural, optical and excitonic properties of MAPbI3 thin films are investigated by using the atomic-force microscopic images, x-ray diffraction patterns, transmittance spectra, photoluminescence spectra and Raman scattering spectra. The experimental results show that the wetting process of MAPbI3 precursor solution on top of the P3CT-Na/ITO/glass substrate can be used to manipulate the molecular packing structure of the P3CT-Na thin film, which determines the formation of MAPbI3 thin films. [ABSTRACT FROM AUTHOR]

—The structural, optical and excitonic characteristics of urea doped CH 3 NH 3 PbI 3 (MAPbI 3) multi-crystalline thin films were investigated by using the X-ray diffraction patterns, atomic-force microscopic images, absorbance spectra, photoluminescence (PL) spectra and Raman scattering spectra. The surface-sensitive Raman scattering spectra show that the urea small molecules are mainly distributed in the top region of the MAPbI 3 thin films and thereby effectively passivating the electron-poor defects (interfacial MA cations) of MAPbI 3 thin films. Besides, the thermal annealing temperature and the concentration of urea additive both strongly influence the formation of MAPbI 3 thin films, which dominates the photovoltaic performance. The use of 5-wt% urea can increase the open-circuit voltage (V OC) and short-circuit current density (J SC) of the MAPbI 3 solar cells from 0.88 V to 19.75 mA/cm2 to 0.94 V and 22.97 mA/cm2, respectively. In addition, the reduced current hysteresis in the J-V curves of the MAPbI 3 solar cells can be explained as due to the effective defect passivation in the top region of the MAPbI 3 thin film by the oxygen-donors of the urea small molecules. Image 1 • The optoelectronic properties of urea-doped MAPbI 3 thin films are investigated. • The 5-wt% urea-doped MAPbI 3 thin film has the disk-like shaped grains. • The urea small molecules are mainly distributed in the top region of MAPbI3 thin films. • The V OC and J SC of MAPbI3 solar cells are simultaneously increased by using the urea additive. [ABSTRACT FROM AUTHOR]