The present study is focused on low-cost preparation of thin film TiO2/CuInS2 nanocomposite three-dimensional (3D) solar cells. With the aid of a simple spray deposition method, we have been able to obtain 3D solar cells, with a remarkable energy conversion efficiency of 5%. The new 3D solar cell design has the potential to breakdown the price barrier and to open up new production technologies for low-cost photovoltaic solar cells.
The major drawback of the present generation of photovoltaic solar cells is their laborious, energy-consuming, and costly production. Therefore, a completely new approach is desirable. With the advent of dye-sensitized (Grätzel-type) solar cells, [1] C 60 /polymer, [2] and hybrid CdSe/polymer bulk heterojunctions, [3] a potential alternative is offered, although some serious complications have still to be tackled. A major concern in these alternatives is their poor stability when operating in full sunlight. The cells must be sealed completely against oxygen and water. All-solid, completely inorganic bulk heterojunctions will not require expensive sealing and have been pursued with limited success so far. Here we report a new approach towards what we call the 3D solar-cell concept. We employed atomic-layer chemical vapor deposition (AL-CVD) to infiltrate CuInS 2 inside the pores of nanostructured TiO 2 . In this way it is possible to obtain a nanometerscale interpenetrating network between n-type TiO 2 and p-type CuInS 2 . Since alignment of the conduction bands is required, an In 2 S 3 buffer layer is applied first. Our cells show photovoltaic activity between 360 and 900 nm with a maximum monochromatic incident photon-to-current conversion efficiency of 80 %. When AM 1.5 irradiation is applied the open-circuit voltage is 0.49 V, the short-circuit current is 18 mA cm ±2 , and the fill factor is 0.44, which converts to an overall energy conversion efficiency of 4 %. This is twice the performance of the best inorganic 3D solar cell reported so far.When pursuing the construction of nanometer-scale interpenetrating networks, one faces the question as to how to obtain such a nanocomposite. This question is even more relevant when n-type and p-type semiconductors are to be blended, since in that case, the concentration of impurities and defects must be kept low and the interfaces need to be passivated. Wet-chemical deposition of CuI [4] and CuSCN [5]
The search for low‐cost thin‐film solar cells, to replace silicon multi‐crystalline cells in due course, calls for new combinations of materials and new cell configurations. Here we report on a new approach, based on semiconductor nanocomposites, towards what we refer to as the three‐dimensional (3D) solar‐cell concept. Atomic layer chemical vapor deposition is employed for infiltration of CuInS2 inside the pores of nanostructured TiO2. In this way it is possible to obtain a nanometer‐scale interpenetrating network between n‐type TiO2 and p‐type CuInS2. X‐ray diffraction, Raman spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, transmission electron microscopy, and current–voltage measurements are used to characterize the nanostructured devices. The 3D solar cells obtained show photovoltaic activity with a maximum monochromatic incident photon‐to‐current conversion efficiency of 80 % and have an energy‐conversion efficiency of 4 %.
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