Solution-Processed Titanium Chelate Used as Both Electrode Modification Layer and Intermediate Layer for Efficient Inverted Tandem Polymer Solar Cells

ABSTRACT Organic polymer solar cells （PSCs） have attracted increasing attention due to light weight, low cost, flexibility and roll-to-roll manufacturing. However, the limited light harvest range of the photoactive layer greatly restrains the power conversion efficiency （PCE） enhancement. In order to expand the light absorption range and further enhance the PCE of the PSCs, tandem structures have been designed and demonstrated. In tandem solar cell, the intermediate layer （IML） plays a critical role in physically and electrically connection of the two subcells. Herein, we apply titanium （diisopropoxide） bis（2,4-pentanedionate） （TIPD） as both electrode modification layer and intermediate layer to investigate the feasibility in inverted tandem polymer solar cells. The same photoactive layers of PTB7-Th：PC71BM are adopted in both front and rear subcells to simplify the evaluation of effectiveness of TIPD layer in tandem structures. By modulating the treatment condition of IML and the thickness of photoactive layer, efficient inverted tandem PSCs have been achieved with minimized voltage loss and excellent charge transportation, giving a best Voc of 1.54 V, which is almost two times that of the single bulk heterojunction （BHJ）-PSC （0.78 V） and an enhanced PCE up to 8.11%.

Strategies toward Highly Efficient Monolithic Perovskite/Organic Tandem Solar Cells

Constructing monolithic tandem solar cells (TSCs) is an effective method to break the Shockley–Queisser (S–Q) radiative efficiency limit for single-junction solar cells. Employing the wide bandgap perovskite materials and low bandgap organic materials as absorber layers for front and rear subcells, respectively, to construct perovskite/organic TSCs can complementarily absorb sunlight in ultraviolet-visible (UV-Vis) range by front perovskite and near-infrared (NIR) range by rear organic molecules, thus reducing the thermalization energy losses. Besides the subcells, the interconnection layer (ICL), which physically and electrically connects the front and rear subcells, is also an important tunnel junction to recombine charges. In this review, we summarize the optimization strategies of wide bandgap perovskites for front subcell, narrow bandgap organic material for rear subcell, and the ICLs employed in monolithic perovskite/organic TSCs.

Topic-Feature Lattices Construction and Visualization for Dynamic Topic Number

The topic recognition for dynamic topic number can realize the dynamic update of super parameters,and obtain the probability distribution of dynamic topics in time dimension,which helps to clear the understanding and tracking of convection text data.However,the current topic recognition model tends to be based on a fixed number of topics K and lacks multi-granularity analysis of subject knowledge.Therefore,it is impossible to deeply perceive the dynamic change of the topic in the time series.By introducing a novel approach on the basis of Infinite Latent Dirichlet allocation model,a topic feature lattice under the dynamic topic number is constructed.In the model,documents,topics and vocabularies are jointly modeled to generate two probability distribution matrices:Documentstopics and topic-feature words.Afterwards,the association intensity is computed between the topic and its feature vocabulary to establish the topic formal context matrix.Finally,the topic feature is induced according to the formal concept analysis(FCA)theory.The topic feature lattice under dynamic topic number(TFL DTN)model is validated on the real dataset by comparing with the mainstream methods.Experiments show that this model is more in line with actual needs,and achieves better results in semi-automatic modeling of topic visualization analysis.

Efficient organic solar cells with low-temperature in situ prepared Ga_(2)O_(3) or In_(2)O_(3) electron collection layers

Facile synthesis of an interfacial layer in organic solar cells (OSCs) is important for broadening material designs and upscaling photovoltaic conversion efficiency (PCE).Herein,a mild solution process of spin-coating In(acac)3and Ga(acac)3isopropanol precursors followed by low-temperature thermal treatment was developed to fabricate In_(2)O_(3)and Ga2O3cathode buffer layers (CBLs).The introduction of In_(2)O_(3)or Ga2O3CBLs endows PM6:Y6-based OSCs with outstanding performance and high PCEs of 16.17%and 16.01%,respectively.Comparison studies present that the In_(2)O_(3)layer possesses a work function (WF) of 4.58 eV,which is more favorable for the formation of ohmic contact compared with the Ga2O3layer with a WF of 5.06 eV and leads to a higher open circuit voltage for the former devices.Electrochemical impedance spectroscopy was performed to reveal how In_(2)O_(3)and Ga2O3affect the internal charge transfer and the origin of their performance difference.Although In_(2)O_(3)possesses lower series resistance loss,Ga2O3has a higher recombination resistance,which enhances the device fill factor and compensates for its series resistance loss to some extent.Comparative analysis of the photo-physics of In_(2)O_(3)and Ga2O3suggests that both are excellent CBLs for highly efficient OSCs.