The conversion of near-infrared (NIR) light into electricity is a crucial goal for advancing the capabilities of dyesensitized solar cells (DSSC). In order to achieve this, two novel squaraine dyes, namely SQI-P and SQI-H, were synthesized and employed as NIR sensitizers in DSSC. These dyes were constructed with a conjugated indoline donor on both sides of the squaraine core, and a long pendant group on the N-position. The strongly donating indoline with phenyl bis-carboxylic anchor groups located in the N-position resulted in a high molar extinction coefficient and a broad absorption spectrum that extended into the NIR region. The experimental results showed that SQI-P/SQI-H sensitizer exhibits strong absorption in the NIR region, improved electron injection efficiency, and excellent photostability. After optimizing the co-sensitized DSSC, the combination of the NIR-absorbing squaraine based-indoline with SQI-P produced a high photocurrent output of 22.3 mA/cm2 at an efficiency of 4.8%. This achievement represents a breakthrough for DSSCs and paves the way for a more efficient future of DSSCs in the NIR region.