Enhancement of the photoelectric performance in inverted bulk heterojunction solid solar cell with inorganic nanocrystals Weiling Luan a,⇑ , Chengxi Zhang a , Lingli Luo a , Binxia Yuan a,b , Lin Jin a , Yong-Sang Kim c a Key Laboratory of Pressure Systems and Safety (MOE), School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, PR China b Shanghai Engineering Research Center of Power Generation Environment Protection, Shanghai University of Electric Power, Shanghai 200090, PR China c School of Electronic and Electrical Engineering, Sungkyunkwan University, Gyeonggi 440-746, Republic of Korea highlights  Solid solar cells based on FeS 2 or PbS NCs showed power conversion efficiency (PCE) of 3.0% and 3.11%, respectively.  The FeS 2 NCs/polymer solar cells showed good time and thermal stability when exposed in air condition.  Ternary solid solar cells based on PbS NCs exhibited a higher short circuit current density (J sc ). article info Article history: Received 4 August 2015 Received in revised form 21 March 2016 Accepted 10 April 2016 Available online 23 April 2016 Keywords: FeS 2 nanocrystals Polymer Solid solar cell Photovoltaic conversion efficiency Stability abstract Nanocrystal/polymer solid solar cells have the advantages of low-cost, simple process, and flexible man- ufacture. In this work, ternary solid solar cells based on FeS 2 and PbS nanocrystals exhibited photovoltaic conversion efficiency of 3.0% and 3.1%, respectively. As a kind of semiconductor with optical absorption in the visible and near-infrared regions, FeS 2 nanocrystals matched well with the solar radiation spectrum. Furthermore, PbS Nanocrystals could increase the number of electrons, due to its multiple exciton effect. Additionally, the FeS 2 nanocrystals solar cells showed high stability, with 83.3% of its initial efficiency remained after 15 weeks of exposure in air, and kept good stable performance at 20–80 °C. The photo- voltaic conversion efficiency fluctuation magnitudes were also found to be smaller than quantum-dot sensitized solar cell under the same conditions. Ó 2016 Published by Elsevier Ltd. 1. Introduction Renewable energy is regarded as an essential supplement to the fossil fuels. Among the various renewable energy resources such as solar energy, wind energy, geothermal energy, biological energy, hydropower, hydrogen energy and wave energy [1], solar energy with the excellent advantages of abundance and non-polluting nat- ure is supposed to be a great potential candidate [2]. Exploitation of solar energy is aimed to convert sunlight/solar radiation into electricity via photovoltaic devices like solar cells. In 1954, Yam- aguchi et al. [3] successfully invented a silicon solar cell with a photovoltaic conversion efficiency (PCE) of 6%, which was regarded as the first generation of solar cells. The second generation of solar cell, the copper indium gallium selenium (CuInGaSe) thin film solar cell, which was developed in early 1989 with its PCE reached up to 13% [4]. However, the further development of these two generation solar cells were restricted owing to the high cost of pure silicon and pollution issues. In recent years, Ito et al. [5] reported a bifacial dye-sensitized solar cell structure with a porous TiO 2 layer that provided high photo-energy conversion efficiency. Near infrared absorption of CdSe x Te 1x alloyed quantum dot [6] was used to pre- pare the quantum dot-sensitized solar cells (QDSSCs). Polymer solar cells based on P3HT, porphyrin-modified ZnO nanorods [7] and self-assembled monolayers [8] have been extensively investi- gated. Nevertheless, DSSCs and QDSSCs show poor stability since their liquid electrolyte leaks, and polymer solar cells with low effi- ciency for the slow electron transmission. Solid cells combined semiconductor NCs and polymers are one of the most promising alternatives to conventional silicon solar cells. In the system of NCs/polymer solid solar cells, both the semi- conductor NCs and the polymers were served as sunlight absorbers and exciton generators as well as electron donor. Electron trans- mission was much faster in NCs than that in polymers. By tuning the size, composition and shape of NCs, the absorption wavelength could be matched with the solar radiation spectrum. Moreover, http://dx.doi.org/10.1016/j.apenergy.2016.04.042 0306-2619/Ó 2016 Published by Elsevier Ltd. ⇑ Corresponding author. E-mail address: luan@ecust.edu.cn (W. Luan). Applied Energy 185 (2017) 2217–2223 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy