Perovskite solar cells (PSCs) have attracted extensive research interest in the last decade due to their high power conversion efficiency (PCE) and simple solution-based fabrication process. [1,2] Evolved from dye-sensitized solar cells (DSSCs), [3] typical PSCs usually employ a mesoporous TiO 2 as the electron-transport layer (ETL), which also functions as the scaffold for depositing the perovskite absorbing layer. [4,5] Although it is criticized that the high-temperature (>450 °C) sintering process for the mesoporous TiO 2 layer makes the device manufacturing complex and energy consumptive, which also hinders the integration of PSCs with flexible substrates and electronics, such mesoscopic PSCs have been dominating the efficiency breakthroughs of PSCs from certified 14.1% in 2013 to 23.7% in 2019. [5-8] The latest 25.2% is highly possible also obtained by mesoscopic PSCs. [9] The ambipolar charge transport characteristics and long charge carrier diffusion length of lead halide perovskites offers the possibility of replacing the mesoporous ETL by a planar one, and constructing planar-structured PSCs with low-temperature (≤150 °C) processes. [10,11] For inverted (p-in) planar PSCs, there are plenty of options available for ETLs and hole-transport layers (HTLs), such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and phenyl-C61-butyric acid methyl ester (PC 61 BM), attributing to years of research on organic solar cells. [12,13] For regular (n-i-p) planar PSCs, compact TiO 2 layer was first used as the ETL, which soon aroused the attention on the anomalous hysteresis phenomenon for PSCs. [14,15] It was claimed that the low electron mobility of compact TiO 2 resulted in charge accumulations at the TiO 2 /perovskite interface and thus caused significant hysteresis. [16,17] Then, it was further found out that the electronic contact between the TiO 2 ETL and the perovskite layer played an essential role in the hysteresis behaviors of PSCs. [18] This is in agreement with the fact that the mesoporous TiO 2-based PSCs usually show much reduced hysteresis, [6,7] since the mesoscopically structured ETL can provide much larger surface area for contacting the perovskite absorber with stabilized properties. Along with the defects at the interfaces, ion migration and trap states in the perovskite layer have also been considered as the origin of the hysteresis Perovskite solar cells (PSCs) have rapidly developed and achieved power conversion efficiencies of over 20% with diverse technical routes. Particularly, planar-structured PSCs can be fabricated with low-temperature (≤150 °C) solution-based processes, which is energy efficient and compatible with flexible substrates. Here, the efficiency and stability of planar PSCs are enhanced by improving the interface contact between the SnO 2 electron-transport layer (ETL) and the perovskite layer. A biological polymer (heparin potassium, HP) is introduced to regulate the arrangement of SnO 2 nanocrystals, and induce vertically aligned crystal growth of perovski...

Traps in the photoactive layer or interface can critically influence photovoltaic device characteristics and stabilities. Here, traps passivation and retardation on device degradation for methylammonium lead trihalide (MAPbI ) perovskite solar cells enabled by a biopolymer heparin sodium (HS) interfacial layer is investigated. The incorporated HS boosts the power conversion efficiency from 17.2 to 20.1% with suppressed hysteresis and Shockley-Read-Hall recombination, which originates primarily from the passivation of traps near the interface between the perovskites and the TiO cathode. The incorporation of an HS interfacial layer also leads to a considerable retardation of device degradation, by which 85% of the initial performance is maintained after 70 d storage in ambient environment. Aided by density functional theory calculations, it is found that the passivation of MAPbI and TiO surfaces by HS occurs through the interactions of the functional groups (COO , SO , or Na ) in HS with undersaturated Pb and I ions in MAPbI and Ti in TiO . This work demonstrates a highly viable and facile interface strategy using biomaterials to afford high-performance and stable perovskite solar cells.

Bacillus subtilis var. natto N21 (Bac; for greater proteolytic capacity) and Saccharomyces cerevisiae Y10 (Sac; for greater acidic capacity) were applied to produce a 2-stage combined fermentation feed. This study investigated whether the enhancement of Bac+Sac fermented feed on broiler growth performance was due to the probiotics per se or due to the fermentation process. Trial 1 included 1-d-old broiler chicks (n=144) randomly assigned to control, water added (same as in the fermentation feed, 23%), and Bac+Sac fermented feed (FBac+Sac) treatments with 4 replicates. Trial 2 included 21-d-old broiler chickens (n=12) assigned into control and FBac+Sac groups for a metabolic trial for nutrient availability. Trial 3 included 1-d-old male broiler chicks (n=216) randomly assigned into 6 treatments with 3 replicates. Treatments included a control, Sac fermented feed (FSac), FBac+Sac, Bac powder (PBac), Sac powder (PSac), and Bac+Sac powder (PBac+Sac). The results from trial 1 showed that FBac+Sac increased BW and feed intake (P<0.05) in 21- and 39-d-old chickens. The water-added group showed decreased BW, weight gain, and feed intake (P<0.05). Trial 2 showed that FBac+ Sac increased gross energy availability (P<0.05). Trial 3 showed that FBac+Sac increased 21- and 39-d-old BW and weight gain (P<0.05). Diets supplemented with probiotic powder or fermented with Sac did not improve broiler growth performance (P>0.05). The growth performance improvement of the FBac+Sac treatment was probably not due to the added water, probiotic powder inclusion, or through single-strain fermentation, but due to the 2-stage fermentation process using Bac and Sac strains.