Update: the deal is now official, new insights below
Samsung has bought a 3% stake in Sharp in a $112 million investment. Sharp is already providing LCD panels (small, medium and large-size ones) to Samsung and this will "further strengthen the alliance" between the two companies. According to some reports Samsung is interested in Sharp's IGZO technology and the two companies may also collaborate on AMOLED and Full-HD LCD technologies.
Other reports and analysts say that this may sign that Samsung intends to divert more energy and finance into OLED TV production and that they seek to outsource more LCD panels from Sharp during the market transition from LCD to OLED. LCD aren't making money anymore and a deal with Sharp may be a good idea for Samsung.
Sharp is a leader in IGZO substrate technology, currently used for LCD panels which the company is already producing. Samsung has also been working on IGZO for a long time but may be seeking a boost in order to start using IGZO in LCD and AMOLED panels, especially large sized OLED TV panels.
Sharp has an active OLED program, and has shown 3.4" IGZO based flexible OLED prototypes at CES 2013. Those OLEDs hae a 540x960 resolution (326 PPI). Previously Sharp has also unveiled a 13.5" QFHD (3840x2160, 326 PPI) OLED panel that uses a WGRB architecture.