| The light absorption layer is a very core part in solar cells, whose performance is significantly influenced by the light absorbing quality, energy-band structure and carrier transport properties of this layer. With the development of nanotechnology, it is widespread concerned that the device performance can be improved by regulating of microstructures. In this paper, by optimizing the morphology of light absorption layers in dye sensitized solar cells (DSSCs) and perovskite solar cells (PSCs), we have studied the correlation between micro/nano structures and photoelectric conversion properties, developed new paths to improve device’s performance.As organic-inorganic composite light-to-electricity transform devices, DSSC has been one of the hottest research points in photovoltaic areas, its highest power conversion efficiency has exceeded 13%. In contrast to tranditional thin-film solar cell, DSSC has the advantages of low cost of raw material, simple production process, low energy consumption and friendly environment, but relatively poor performance still hinder it from industrial operations. In DSSCs, the working electrode which is composed of mesoporous semiconductor film and dye plays the roles of light harvesting and transporting photogenerated electron. To enhance one-dimensional electron transport while keeping high surface area of semiconductor film, we fabricated one-dimensional assembly of TiO2 nanoparticles (NPs) by an improved electrospinning technique. The newly developed 1D assembly of nanoparticles (AS-NP) has been introduced into the photoanode in DSSCs. Compared to the traditional disordered stacking of TiO2 NPs, the AS-NPs bring in faster charge transport and longer electron lifetime, as well as a higher light scattering ability. It is exhibited that the AS-NPs can enhance electron transport and light scattering, while retaining the merits of NP morphology. Consequently, the efficiency of a cell based on an AS-NP/NP bilayer photoanode could be improved by about 15% in comparison to a reference cell made of absolute TiO2 NPs.Perovskite solar cells, which developed on the base of DSSCs, have received much attention recently because of their high power conversion efficiency. But their performance is influenced greatly by ambient humidity during preparation process, because organic-inorganic perovskite compounds are hygroscopic and the microstructures of perovskite films are sensitive to moisture. To understand the phenomenon, we investigated the influence of ambient humidity on crystallization and surface morphology of one-step spin-coated perovskite films, as well as the performance of solar cells based on these perovskite films. It is found that the influence of ambient humidity on nucleation at spin-coating stage is quite different from that on crystal growth at annealing stage. At the spin-coating stage, high nucleation density induced by high supersaturation prefers to appear under anhydrous circumstances, resulting in layer growth and high coverage of perovskite films. But at the annealing stage, the modest supersaturation benefits formation of perovskite films with good crystallinity. The films spin-coated under low relative humidity followed by annealing under high RH show an increase of crystallinity and improved performance of devices. Therefore, a mechanism of fast nucleation followed by modest crystal growth is suggested in the formation of high-quality perovskite films. These insights into the perovskite crystallization affected by moisture may aid in further improvement and understanding of the devices. |
