Low-Temperature Solution-Processed ZnSe Electron Transport Layer for Efficient Planar Perovskite Solar Cells with Negligible Hysteresis and Improved Photostability.

For a typical perovskite solar cell (PKSC), the electron transport layer (ETL) has a great effect on device performance and stability. Herein, we manifest that low-temperature solution-processed ZnSe can be used as a potential ETL for PKSCs. Our optimized device with ZnSe ETL has achieved a high power conversion efficiency (PCE) of 17.78% with negligible hysteresis, compared with the TiO2 based cell (13.76%). This enhanced photovoltaic performance is attributed to the suitable band alignment, high electron mobility, and reduced charge accumulation at the interface of ETL/perovskite. Encouraging results were obtained when the thin layer of ZnSe cooperated with TiO2. It shows that the device based on the TiO2/ZnSe ETL with cascade conduction band level can effectively reduce the interfacial charge recombination and promote carrier transfer with the champion PCE of 18.57%. In addition, the ZnSe-based device exhibits a better photostability than the control device due to the greater ultraviolet (UV) light harvesting of the ZnSe layer, which can efficiently prevent the perovskite film from intense UV-light exposure to avoid associated degradation. Consequently, our results present that a promising ETL can be a potential candidate of the n-type ETL for commercialization of efficient and photostable PKSCs.

Combination of Carrier Concentration Regulation and High Band Degeneracy for Enhanced Thermoelectric Performance of Cu3SbSe4.

The effect of Al-, Ga-, and In-doping on the thermoelectric (TE) properties of Cu3SbSe4 has been comparatively studied on the basis of theoretical prediction and experimental validation. It is found that tiny Al/Ga/In substitution leads to a great enhancement of electrical conductivity with high carrier concentration and also large Seebeck coefficient due to the preserved high band degeneracy and thereby a remarkably high power factor. Ultimately, coupled with the depressed lattice thermal conductivity, all three elements (Al/Ga/In) substituted samples have obtained a highly improved thermoelectric performance with respect to undoped Cu3SbSe4. Compared to the samples at the same Al/In doping level, the slightly Ga-doped sample presents better TE performance over the wide temperature range, and the Cu3Sb0.995Ga0.005Se4 sample presents a record high ZT value of 0.9 among single-doped Cu3SbSe4 at 623 K, which is about 80% higher than that of pristine Cu3SbSe4. This work offers an alternative approach to boost the TE properties of Cu3SbSe4 by selecting efficient dopant to weaken the coupling between electrical conductivity and Seebeck coefficient.

A new method for simultaneous measurement of Seebeck coefficient and resistivity.

A new method has been proposed and verified to measure the Seebeck coefficient and electrical resistivity of a sample in the paper. Different from the conventional method for Seebeck coefficient and resistivity measurement, the new method adopts a four-point configuration to measure both the Seebeck coefficient and resistivity. It can well identify the inhomogeneity of the sample by simply comparing the four Seebeck coefficients of different probe combinations, and it is more accurate and appropriate to take the average value of the four Seebeck coefficients as the measured result of the Seebeck coefficient of the sample than that measured by the two-point method. Furthermore, the four-point configuration makes it also very convenient to measure the resistivity by using the Van der Pauw method. The validity of this method has been verified with both the constantan alloy and p-type Bi2Te3 semiconductor samples, and the measurement results are in good agreement with those obtained by commercial available equipment.